Method and circuit for indicating quality and accuracy of physiological measurements

Abstract

Sensors and monitors for a physiological monitoring system having capability to indicate an accuracy of an estimated physiological condition. The sensor senses at least one physiological characteristic of a patient and is connectable to a monitor that estimates the physiological condition from signals detected by the sensor. The sensor includes a detector for detecting the signals from the patient which are indicative of the physiological characteristic. The sensor is associated with a memory configured to store data that defines at least one sensor signal specification boundary for the detected signals. The boundary is indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor. The sensor further includes means for providing access to the memory to allow transmission of the data that defines the at least one sensor boundary to the monitor.

What is claimed is: 
     
       1. A system comprising a sensor and a monitor for sensing at least one physiological characteristic of a patient, the sensor being connectable to a monitor that estimates a physiological characteristic from signals detected by the sensor, the sensor comprising:
 a detector for detecting the signals from the patient which are indicative of the physiological characteristic; 
 a memory connected with the sensor, said memory being physically located on one of a sensor body, sensor cable, sensor connecting plug or a sensor adapter module, and said memory being configured to store data defining at least one sensor signal specification boundary for the detected signals, the sensor signal specification boundary being indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor, wherein the sensor signal specification boundary includes limits for an AC modulation component and DC component of the signals; and 
 means for providing access to the memory to allow transmission of the data defining the at least one sensor boundary to the monitor; 
 wherein the monitor determines to display or not display the estimate of the physiological characteristic based on the signals and their relationship relative to a plurality of sensor signal specification boundaries and to a plurality of monitor boundaries preprogrammed into the monitor. 
 
     
     
       2. The system of  claim 1 , wherein the monitor computes calculated values, having AC and DC components, from the signals, wherein the sensor signal specification boundary constitutes limits on the AC and DC components of the calculated values, and wherein the AC and DC components are dependent on either a physiological status of the patient, sensor type, or sensor location. 
     
     
       3. The system of  claim 1 , wherein the signals detected from the patient include first and second sets of signals derived from detected light scattered from the patient, the light having fist and second wavelengths, the signals derived from detected light each having an AC modulation component and a DC component, and the sensor signal specification boundary including limits on the AC and DC components. 
     
     
       4. The system of  claim 3 , wherein the signals derived from detected light are indicative of an arterial oxygen saturation of the patient. 
     
     
       5. The system of  claim 1 , wherein the memory comprises a digital memory configured to store a digital representation of the at least one sensor signal specification boundary, and wherein the physiological characteristic is arterial oxygen saturation. 
     
     
       6. A monitor for providing an indication of an accuracy of an estimated physiological condition of a patient, the monitor being connectable to a sensor that detects signals indicative of at least one physiological characteristic of the patient, the monitor comprising:
 a receiving circuit configured to receive the signals indicative of the at least one physiological characteristic from the sensor and data defining at least one sensor signal specification boundary for the detected signals from the sensor, the sensor signal specification boundary being indicative of a quality of the signals detected by the sensor and an accuracy of the physiological characteristic estimated from the detected signals, wherein the at least one sensor boundary is indicative of a transition between a signal regime considered normal for the sensor in its usual application and a signal regime considered to be abnormal; 
 a processing circuit configured to estimate the physiological condition of the patient based on the received signals, compare the received signals against the at least one sensor boundary, and generate the indication of the accuracy of the estimated physiological condition, wherein the processing circuit is further configured to determine whether the received signals are within the normal regime or the abnormal regime; and 
 means for providing the indication of the accuracy of the estimated physiological condition to a user of the monitor, 
 wherein said processing circuit determines to display or not display the estimate of the physiological characteristic based on the signals and their relationship relative to a plurality of sensor signal specification boundaries and to a plurality of monitor boundaries preprogrammed into the monitor. 
 
     
     
       7. The monitor of  claim 6 , wherein said normal regime is one in which the sensor is likely to be properly applied to the patient and said abnormal regime is one in which the sensor may have partially or entirely come off the patient. 
     
     
       8. The monitor of  claim 6 , wherein the processing circuit is further configured to compute an indication of whether the sensor is likely to be applied to the patient or has partially or entirely came off the patient. 
     
     
       9. A system comprising a sensor and a monitor for sensing at least one physiological characteristic of a patient, the sensor being connectable to a monitor that estimates the physiological characteristic from signals detected by the sensor, the sensor comprising:
 a detector for detecting the signals from the patient which are indicative of the physiological characteristic; 
 a memory connected with the sensor, said memory being physically located on one of a sensor body, sensor cable, sensor connecting plug or a sensor adapter module, and said memory being configured to store data defining at least one sensor signal specification boundary for the detected signals, the sensor signal specification boundary being indicative of a transition between a signal regime considered normal for the sensor in its usual application, and a signal regime considered to be abnormal, in which said sensor signal specification boundary is characteristic of a model of the sensor, and said boundary is characteristic of individual components used in making the sensor; and 
 means for providing access to the memory to allow transmission of the data defining the at least one sensor boundary to the monitor, 
 wherein the monitor determines to display or not display the estimate of the physiological characteristic based on the signals and their relationship relative to a plurality of sensor signal specification boundaries and to a plurality of monitor boundaries preprogrammed into the monitor. 
 
     
     
       10. The system of  claim 9  wherein the monitor is a pulse oximetry monitor having means to determine whether the signals are within said normal regime or said abnormal regime; and means for informing a user of the system as to whether the signal is normal or abnormal. 
     
     
       11. The system of  claim 10  wherein said means for informing the user is an alarm that is triggered when the signal moves from said normal regime to said abnormal regime. 
     
     
       12. The system of  claim 10 , wherein said normal regime is one in which the sensor is likely to be properly applied to the patient and said abnormal regime is one in which the sensor may have partially or entirely come off the patient.